Transparent PNG casting square shadow

[AMG445]

Hi guys, in every other version of Vray this has not been an issue, but with the latest version, if you have a transparent PNG (In this case an ivy) the transparent part of the PNG is fine (As diffuse Alpha is checked) but the actual rectangle the png is on casts a square shadow (cast shadows has been turned off).
As mentioned - previous versions worked perfectly with no issues. Any help would be appreciated,
Thanks in advance,
Nick

[kenancakir]

You should aply the same texture to the back face..

[AMG445]

Thanks very much, that worked perfectly - much appreciated, Nick

[konstantin_chaos]

Hi guys,

Just to clarify why this is happening:
V-Ray samples the scene by shooting rays from the camera and tracing them in the scene.
To shade the wall behind the plane V-Ray has to trace a ray through the transparent surface, 'bounce' it off the wall and then evaluate lighting and reflections.
When one side of the plane is transparent and the other one opaque, the ray passes through but the bunce-light rays are hitting the opaque backside of the surface.
This is causing occlusion behind the entire surface.

We were actually considering adding a global option that tells V-Ray to ignore all back-face materials and automatically apply the front shader to the back.
Do you guys think this might be something useful?
How often do you rely on different back-face materials in your scenes?

Konstantin

[kenancakir]

We were actually considering adding a global option that tells V-Ray to ignore all back-face materials and automatically apply the front shader to the back.
Do you guys think this might be something useful?
How often do you rely on different back-face materials in your scenes?

Konstantin

Hi, i have never need different materials on front and back faces, for me the global option you mentioned would be very helpful.. Thanks..

[fixeighted]

Oddly this is similar to a Max post today https://forums.chaosgroup.com/forum/...-casts-shadows

In case it is useful here also, when the surface under the opacity has a blurry reflection then this will still occur.
The only way I can get it to work as expected is not to use opacity but instead use refraction.